The absolute age of the globular cluster M15 using near-infrared adaptive optics images from PISCES/LBT

TL;DR

This study uses advanced near-infrared adaptive optics imaging from the LBT to accurately determine the age of the globular cluster M15, demonstrating the technique's effectiveness comparable to space-based observations.

Contribution

The paper introduces the use of LBT's adaptive optics system with PISCES camera for deep NIR photometry of M15, achieving high-quality data comparable to space telescopes.

Findings

Age of M15 is approximately 13 Gyr.

Adaptive optics imaging improves limiting magnitude by ~2 mag.

LBT data quality rivals space-based observations.

Abstract

We present deep near-infrared (NIR) J, Ks photometry of the old, metal-poor Galactic globular cluster M\,15 obtained with images collected with the LUCI1 and PISCES cameras available at the Large Binocular Telescope (LBT). We show how the use of First Light Adaptive Optics system coupled with the (FLAO) PISCES camera allows us to improve the limiting magnitude by ~2 mag in Ks. By analyzing archival HST data, we demonstrate that the quality of the LBT/PISCES color magnitude diagram is fully comparable with analogous space-based data. The smaller field of view is balanced by the shorter exposure time required to reach a similar photometric limit. We investigated the absolute age of M\,15 by means of two methods: i) by determining the age from the position of the main sequence turn-off; and ii) by the magnitude difference between the MSTO and the well-defined knee detected along the faint portion of the MS. We derive consistent values of the absolute age of M15, that is 12.9+-2.6 Gyr and 13.3+-1.1 Gyr, respectively.